The invention relates to an apparatus for measuring state variables with at least one fiber-optic sensor, containing at least one optical coupler, at least one filter element and at least one photoelectric converter. The invention also relates to a method for producing such an apparatus and the use thereof.
EP 1 826 545 A2 discloses an apparatus of the above mentioned type. The apparatus uses an optical waveguide which is laid in or along a mechanical component. The optical waveguide has a plurality of fiber Bragg gratings. Each fiber Bragg grating reflects part of an optical input signal running in the optical waveguide. Upon the influence of a mechanical stress, the length of the optical waveguide and thus the grating constant of the fiber Bragg grating will change. As a result, the reflected wavelength changes as well, and therefore it is possible to extrapolate to the stress and/or the temperature of the mechanical component from an evaluation of the reflected optical output signal.
In order to generate and evaluate the optical signal, it is known to use a wide band light source, an optical circulator and an arrayed waveguide grating. These components are joined as discrete devices with known optic connectors or splices. However, this approach has the drawback that the apparatus for generating and evaluating signals shows little mechanical robustness. Furthermore, the space required and the energy consumed are comparatively great, and therefore this known apparatus can only be produced and operated with considerable expenditure.
Based on this known apparatus, the object of the invention is thus to provide an apparatus for measuring state variables, which makes do with a small space available and can be produced and used in simple and cost-effective way.